1. Field of the Invention
The invention relates to vacuum containers fabricated from synthetic polymeric resins.
2. BRIEF DESCRIPTION OF THE PRIOR ART
A wide variety of vacuum containers fabricated from synthetic polymeric resins are used to contain an equally wide variety of materials. The advantages of such containers over earlier fabrications from glass, metal and like substances are well recognized and include a reduction in weight.
An example of a material advantageously contained under a vacuum is a foodstuff. In this case, the vacuum in the container may be established in a hot-fill application, i.e., when the food material for containment is placed in the container while it is at a high temperature, in comparison to the storage temperature of the container. Examples of such hot-fill applications include the packaging of foods, such as jams, baby juice and the like. As the container contents cool, the content volume decreases at a greater rate than the resin container, thereby creating a vacuum within the sealed container.
The container of the present invention is an improvement in the art, providing visible (and at times audible) means of ascertaining its vacuum integrity. In addition, the containers of the invention may be fabricated from thinner, lighter films of synthetic polymeric resins without encouraging "paneling" when the vacuum is established. Paneling is the total or partial collapse of a container structure which may occur when the container walls are not sufficiently strong to resist deformation if there is a pressure differential between the container internally and externally. The deformation or collapse may even be severe enough to cause a rupture of the total container. More frequently however there is a partial collapse, including in a multi-layer container, the rupturing of any of the layers or the loss of adhesion between layers. Such failure renders the container useless for many purposes.
In blown film containers of the invention, critical sealing areas such as the bottom pinch-off and the parting line are relieved of added stress from the delta pressure.
All of the above advantages associated with the containers of the invention are economic in nature and additionally provide added safety to the consumer who purchases materials packaged in the containers of the invention. Safety is found in the tamper-proof, vacuum indicators provided in the containers of the invention.